1. Field of the Invention
The present invention relates to a joint, and more particularly to a clearance take-up joint for a seat adjustable mechanism and which can prevent any possible shaking of the seatback with respect to the seat.
2. Description of Related Art
Clearance take-up joints are used with seatback adjustment mechanisms, seat height adjustment mechanisms and power windows to eliminate the clearance between gear assemblies. With reference to FIGS. 8 and 9, a conventional clearance take-up joint in accordance with the prior art comprises a stationary gear plate (60), a rotary gear plate (70), a gear coupler (80) and two discs (82). The joint is particularly suited for use with a seatback adjustment mechanism. Each gear plate (60, 70) has teeth (61, 71) formed on the inner periphery of the gear plate (60, 70). The rotary gear plate (70) is supported by a bearing race (73), with multiple ball bearings (72) mounted between the gear plate (70) and the bearing race (73).
The gear coupler (80) has two sets of teeth (not numbered) formed on the outer periphery of the gear coupler to respectively mesh with the teeth (61, 71) of the gear plates (60, 70). A central bore (81) is defined in the gear coupler (80) to mount the pair of discs (82).
Each disc (82) has a central hole (821) through which a shaft (90) is installed. A hollow notch (822) is formed at the lower portion of the central hole (821) in each disk (82). An arcuate window (823) is formed in each disk (82) to collectively hold a resilient member (83) that presses one of the discs (82) to the right and the other of the discs (82) to the left. In addition, the shaft (90) has a lug (91) that extends into the hollow notches (822) in the two discs (82).
When the shaft (90) is stationary, the discs (82) will be pushed by the force provided by the resilient member (83) to be offset to each other and to abut the inner surface of central bore (81) in the gear coupler (80). Some teeth on the gear coupler (80) will mesh with the teeth (61, 71) in the gear plates (60, 70). Consequently, the gear plates (60, 70) will not rotate relative to each other due to the engagement of the teeth (61, 71) of the gear plates (60, 70) and the gear coupler (80). The inclination of the seatback relative to the seat is fixed.
When the shaft (90) is turned, the lug (91) on the shaft (90) will push the hollow notch (822) in one of the discs (82) to rotate to overlap with the other disc (82) more. Consequently, a gap will be defined between the inner surface of the central bore (81) of the gear coupler (80) and the discs (82). A clearance will occur for the teeth on the gear coupler (80) to release from the teeth (61, 71) in the gear plates (60, 70). Consequently, the rotary gear plate (70) can freely rotate relative to the stationary gear (60). The inclination of the seatback can be adjusted.
From the foregoing, it is clear that this conventional joint has the disadvantage of the existence of friction between the discs (82) themselves and between the discs (82) and the gear plates (60, 70). If the friction is larger than the force produced by the resilient member (83) that outspreads the gear plates (60, 70), excessive clearance will occur between the meshing teeth of the gear coupler (80) and the teeth (61, 71) of the gear plates (60, 70). Therefore, the seatback may shake with respect to the seat.
Furthermore, because the resilient member (83) is arranged in the arcuate windows (823) in the discs (82), two ends of the resilient member (83) are respectively located at different longitudinal levels. To install the resilient member (83) in the discs (82) is difficult. In addition, the resilient member (83) will deform irregularly, and the resilient member""s (83) elasticity will be lost in a short time. The resilient member (83) cannot provide an enough outspreading or expanding force to the discs (82), and a gap will be generated between the gear coupler (80) and the teeth (61, 71) of gear plate (60, 70). The seatback easily shakes with respect to the seat.
To overcome the shortcomings, the present invention tends to provide an improved clearance take-up joint to mitigate or obviate the aforementioned problems.
The main objective of the invention is to provide an improved joint for adjusting the inclination of a seatback, which can prevent any shaking of the seatback with respect to the seat. The clearance take-up joint has a first leaf, a second leaf, a driving wedge-shaped disk and two driven wedge-shaped segments. A block with an outer wedge-shaped resistant surface is formed on the driving wedge-shaped disk. A wedge arrangement is formed between the supporting base and each segment to raise the segment as the driving wedge-shaped disk is rotated with a shaft. Therefore, each segment is moved in the axial direction along the driving wedge-shaped disk by means of the wedge arrangement between the supporting base and the segment. Sufficient clearance will occur between the meshing teeth of the gears so as to unlock the second leaf from the first leaf, which ensures the smooth rotation of the second leaf with respect to the first leaf. The angle between the second leaf and the first leaf can be adjusted.